Reduction Studies on Mixed Chelate Complexes

Robert J. Balahura, Nita A. Lewis

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The Cr2+ reductions of the complexes [Co(en)(ptdn)2]+, [Co(en)2(ptdn)]2+, and [Co(en)3]3+ have been studied. The reaction of [Co(en)(ptdn)2]+ proceeded by three pathways: inner-sphere monobridged (k25°C = (2.5 ± 0.2) × 10-3 M-1 s-1, ΔH = 13.7 ± 0.9 kcal mol-1, ΔS = -24 ± 3 eu), inner-sphere dibridged (k25°C = (2.1 ± 0.2) × 10-3 M-1 s-1, ΔH = 13 ± 1 kcal mol-1, ΔS = -28 ± 5 eu), and outer sphere (k25°C = (2.0 ± 0.2) × 10-3 M-1 s-1, ΔH = 10 ± 2 kcal mol-1, ΔS = -36 ± 7 eu); μ = 1.0 M (LiClO4). The [Co(en)2(ptdn)]2+ complex was reduced by Cr2+ with k50°C = 5.7 × 10-5 M-1 s-1, μ = 1.0 M (LiClO4). This reaction was shown to occur partially by an inner-sphere path. For [Co(en)3]3+ only an outersphere path is possible and k50°C = 1.1 × 10-4 M-1 s-1, μ = 1.0 M (LiClO4). Rate trends within the series [Co(ptdn)3], [Co(en)(ptdn)2]+, [Co(en)2(ptdn)]2+, and [Co(en)3]3+ as well as within the analogous oxalato-Co(III) complexes are discussed in terms of ligand field effects.

Original languageEnglish (US)
Pages (from-to)4716-4721
Number of pages6
JournalJournal of the American Chemical Society
Volume99
Issue number14
DOIs
StatePublished - Jan 1 1977
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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